There are numerous ways of attaching fencing material to posts, the most common being by fastening means in the form of nails, rivets, screws, bolts, wire, or straps. In stringing the fencing material, stretchers are used and as each section between posts is pulled taut, the fastening elements are driven into the post or wrapped about it, as the case may be. The aforesaid fastening means deteriorate rapidly due to stress, vibration, weathering and the like, and the anchoring is seldom firm enough to withstand snow and wind loading. A more durable system of attaching is with the air of lockbars comprised of non-corrosive metal material designed to be attached by bolts or screws or by means of clamps to the post over the fencing, the post being especially designed to have the lockbars attached thereto. The use of lockbars is expensive because not only do the lockbars themselves have to be specially prepared, but also the posts; is cumbersome and require time-consuming installation procedures. The attaching structures as herein described are designed to be durable, relatively inexpensive compared to the lockbars referred to above, easy to install and, beyond this, to impart tension to the section of fencing between posts as a result of the installation procedure. Further, the structures are adapted not only to attaching fencing to posts, but have a more general application in that they can be used very effectively for stretching and attaching substantially any kind of flexible webbing, screening, fabric, sheeting or the like to spaced structural members for various purposes, rapidly without the necessity for fasteners, tools or specialized skills on the part of the installer. Additionally, the structures are capable of being manufactured by conventional methods of extrusion, protrusion, casting, rolling and the like from metal, alloys of metal, plastics, and in a variety of sizes, shapes and heights inexpensively and rapidly.